Embodiments of inventive concept relate to semiconductor devices and methods of manufacturing the same, and more particularly, to semiconductor devices including devices having a plurality of operational voltages, and methods of manufacturing the same.
Integrated circuit devices may be formed on a surface of a semiconductor substrate. Metal oxide semiconductor (MOS) devices constituting semiconductor circuits may be separated from each other by a device isolation layer structure formed near a surface of the semiconductor substrate. The device isolation layer may include a field oxide layer formed using a local oxidation of silicon (LOCOS) method, and/or a shallow trench isolation (STI) layer formed using a STI method, in which an insulating layer buried in a trench is used. The STI layer may provide a substantially flat surface for post-processing without having a “bird's beak”, in contrast to a field oxide layer formed using the LOCOS method, and thus the STI layer may be used as an alternative for a field oxidation layer to cope with the size of the semiconductor integrated circuits being reduced to an order of sub-microns or less.
Due to recent developments in semiconductor manufacturing technology, a plurality of field effect transistors (FETs) operating at different threshold voltages may be provided in a single semiconductor device, and semiconductor devices that are compact and perform various functions are gaining attention. For example, the semiconductor device may include logic devices, memory devices such as dynamic random access memory (DRAM) devices and/or static random access memory (SRAM) devices, digital signal processors, and/or devices in which these devices are converged. The STI layer may be used for the integration of such semiconductor devices.